This application is a division of application Ser. No. 07/596,580 filed Oct. 10, 1990, now U.S. Pat. No. 5,151,529, issued Sep. 29, 1992, which is a continuation-in-part of application Ser. No. 07/440,235 filed Nov. 22, 1989, now abandoned.
The present invention relates to a series of new compounds, to which we have assigned the class name "Phomactin". These compounds may be produced by cultivation of an appropriate microorganism (fungus) of the genus Phoma. The invention also provides a fermentation process for producing these compounds using a novel strain of microorganism of the genus Phoma, as well as the new strain itself, and provides methods and compositions using the new compounds of the invention as platelet activating factor antagonists.
"Platelet activating factor" is herein abbreviated, as is conventional, to "PAF".
Natural PAF, at least as isolated from mammalian tissues, is a mixture of from 2 to 5 phospholipids, the number depending upon the nature of the original tissue. The major constituents of PAF may be represented by the formula (A): ##STR1## in which R represents a log chain aliphatic hydrocarbon group, which may be saturated or unsaturated. Natural PAF is levorotatory and the various components of natural PAF may be identified, for example as: l-C.sub.16:0 =formula (A) where R represents a hexadecyl group: l-C.sub.18:0 =formula (A) where R represents an octadecyl group: or l-C.sub.18:1 =formula (A) where R represents a 9(Z-octadecenyl group. The convention used above for identifying the constituents of PAF gives the rotation first (l, in the above examples), followed by the number of carbon atoms, and finally the number of double bonds.
PAF exhibits a strong platelet activating and aggregating effect, from which it derives its name. It has, however, in recent years been seen to be a potentially crucial mediator in a wide variety of pathological processs. Thus, it also has a hypotensive effect and increases vasopermeability; it is believed to be an active agent in the induction of the shock state (for example endotoxin-induced shock) and to act as a mediator of inflammatory disease. It has also been found to play a role in cardiac and systemic anaphylaxis, gastric and intestinal ulceration, psoriasis and immune and renal disorders.
It is not, therefore, surprising that, as a result, PAF antagonists have been investigated with a view to developing new types of treatment for the above pathologies, and notably new types of anti-shock agent and anti-inflammatory agent. Accordingly, various compounds have been investigated in an attempt to find such PAG antagonists, and, currently, several compounds are known as PAF antagonists. Although the chemical structure of known PAF antagonists varies widely, and there appears to be no obvious common factor linking their chemical structures, in general, known materials having PAF-antagonist activity may be classified according to their chemical structure as either PAF type or non-PAG type compounds. Of the known compounds. PAF type antagonists are mostly prepared by chemical synthesis, whilst non-PAF type antagonists are mostly recovered from the secondary metabolites of plants and microorganisms. Examples of compounds of the non-PAF type include, for example, ginkgolide (isolated from Ginkgo biloba), kadzurenone (isolated from Piper futokadzura), veraguensin (isolated from Magnolia acuminata), galbengin and galbrabin (isolated from Himantandra velgravena), nectandrin A and B (isolated from Nectandra rigida), burseran (isolated from Bursera microphlla) [details of the above compounds are given by P. Braquet and J. J. Godfroid: Trends in Pharm. Sci., Vol. 7, pp. 397 et seq (1986)], a gliotoxin derivative [isolated from Penicillium terlikowskii: M. Okamoto, Chem. Pharm. Bull., 34, 340 (1986)] and a diketopiperazine derivative [isolated from Streptomyces sp.: S. Takase, J. Org. Chem., 52, 3485 (1987)].
A variety of PAF-type compounds are known, but these are not relevant to the present invention.
A review of the nature and uses of PAF antagonists is given by P. Braquet et al., Trends in Pharm. Sci., Vol. 10, pp. 23 et seq (1989). Braquet et al examined the effect of BN-52021 (5 mg kg.sup.-1, given 15 min before coronary artery occlusion) on arrhythmias in mongrel dogs. As shown in Table I, BN-52021 significantly reduced the number of ectopic beats during the 30 min ischemic period. In addition, preliminary studies in rats subjected to coronary artery ligation have shown that BN-52021 (5 mg kg.sup.-1, i.v. immediately before occlusion), significantly reduced the infarct size as assessed by histological examination after 24 h of occlusion. In the control group the infarct size was 26.+-.2.2% of heart tissue, whereas in the BN-52021-treated group this value was reduced to 17.+-.1.8% (p&lt;0.05). ##STR2##
TABLE I __________________________________________________________________________ Effect of BN-52021 on arrhythmias evoked by ligation of left anterior descending coronary artery in dogs anesthetized with halothane Number of ectopic beats during 30 min of ischemia, mean .+-. SEM Treatment .eta. 5-10 10-15 15-20 20-25 25-30 min __________________________________________________________________________ Control 18 106 .+-. 26.0 119 .+-. 33.4 208 .+-. 41.8 355 .+-. 69.5 473 .+-. 104.8 BN-52021 7 10 .+-. 5.4* 10 .+-. 5.3* 15 .+-. 6.3* 55 .+-. 28.6* 98 .+-. 39.0* __________________________________________________________________________ These cumulative data represent the sum of single ventricular extrasystoles in salvos, and ventricular tachycardia. BN52021 was introduced in an i.v. bolus of 5 mgkg.sup.-1 15 min before coronary arter ligation. *.rho. &lt; 0.05 (Wilcoxon test).
We have now discovered a series of new PAF-antagonist compounds of the non-PAF type, which we have in accordance with current convention, named "the phomactins", and which can be produced by the cultivation of a microorganism, which we have identified as SANK 11486, which belongs to the species Phoma and which has been isolated from the shells of certain crabs.